How to clean carpet stains and pet urine without the lingering smell

Carpet is a good place for accidents to hide. Spills and pet urine sink into the fibers, then into the underlay, and sometimes through to the floor beneath. The surface can look clean long after the smell has started, and a stain that was dried by the heating can come back as soon as the room warms up or the carpet is damp. The key to dealing with carpet stains is to treat the stain quickly, to use the right cleaner for the type of stain, and to dry the carpet and the underlay fully.

Pet urine needs its own approach. It contains uric acid and salts that a normal carpet cleaner does not remove, and ammonia-based products make the problem worse. An enzyme cleaner breaks down the compounds that cause the smell, and it works best when it is applied generously and given time.

What you need

• Clean white cloths or paper towels, in quantity
• Cold water
• An enzyme cleaner made for pet urine, for urine stains
• A carpet cleaner made for general stains, for other spills
• A spray bottle
• A wet and dry vacuum, if you have one, or a dry towel and a fan
• A UV or black light flashlight, for finding old urine
• Masking tape, for marking spots

Acting quickly on fresh stains

Speed matters more than anything else. A fresh spill is much easier to remove than one that has dried.

1. Blot the spill with a clean white cloth or paper towel. Press down firmly and lift, moving to a clean part of the cloth each time. Do not rub, because rubbing pushes the stain deeper into the fibers and spreads it.
2. Continue blotting until the cloth comes away clean or nearly clean.
3. Rinse the area with a small amount of cold water, blot again, and repeat until the water runs clear.
4. For a food or drink stain, use a carpet cleaner made for general stains, following the label. Test it on a hidden spot first, because some dyes can bleed.
5. Dry the area. Put a dry towel on the spot and stand on it, or press down with a heavy book, then run a fan over the area until it is dry.

Cold water is the right choice for most stains. Hot water can set some protein and tannin stains, such as blood, milk and tea, so keep to cold.

Removing pet urine

Pet urine needs more time and a different cleaner.

1. Blot up as much of the fresh urine as you can, pressing with a dry cloth until it stops coming up.
2. Rinse the area with cold water and blot again. This dilutes the urine and removes some of the salts.
3. Spray the enzyme cleaner generously on the stained area. Use enough to soak the carpet and reach the underlay beneath the spot, but not so much that it runs onto the wood or the walls.
4. Leave the cleaner to work for the time the label gives. Many enzyme cleaners need fifteen minutes or more, and some need a day. Keep the area damp during this time, by covering it with a damp cloth if needed.
5. Blot the area dry, then rinse with cold water and blot again.
6. Dry the carpet fully with a fan or with a wet and dry vacuum. Urine that remains in the underlay will bring the smell back as the carpet warms and dries.

Do not use ammonia or ammonia-based cleaners on pet urine. The ammonia smells like urine to an animal, and a cat or dog may return to the same spot to mark it again.

Finding old urine

Old pet urine is often invisible, but it can still smell, and it can still attract repeat marking. A UV or black light flashlight shows dried urine as a faint glow, and it is the best way to find the spots you cannot smell.

Turn off the room lights, and sweep the flashlight slowly over the carpet, the edges by the baseboard and the areas where the pet likes to lie. Mark each spot you find with a small piece of masking tape. Then treat each marked spot with the enzyme cleaner, as described above, and dry it properly. Treat the spots even when the carpet looks clean, because the urine will be in the padding beneath.

When the urine has reached the underlay

Urine that has soaked through the carpet and into the underlay is harder to remove. The underlay acts like a sponge, and an enzyme cleaner on the surface may not reach it.

If the area smells strongly after treatment, lift a corner of the carpet and check the underlay. If the underlay is stained or smells strongly, it may need replacing. Some carpet specialists can inject an enzyme cleaner into the underlay, but a severe case may need the underlay and the affected section of carpet removed and replaced. Check that the subfloor is not damaged before you decide, because urine that reaches a wooden or chipboard subfloor can cause long-term damage.

Other carpet stains

• Wine and coffee. Blot, rinse with cold water, and use a general carpet cleaner. Repeat until the stain lifts.
• Blood. Blot with cold water only, never hot, and use a cleaner for protein stains if the first rinse does not lift it.
• Grease. Blot to lift the excess, then apply a small amount of dish soap diluted in cold water, blot, and rinse.
• Vomit. Scrape off solid matter with a spoon, then blot and treat with an enzyme cleaner, because the acids can leave a lasting smell.
• Ink. Dab with rubbing alcohol on a clean cloth, testing first on a hidden spot, and blot until the ink lifts. Rinse and dry.

Drying the carpet

Drying is the step people skip, and it is often the reason a stain or smell returns. Carpet and underlay take a long time to dry, especially in a damp room. Run a fan over the area, open a window if the air is dry outside, and use a dehumidifier if the room is humid. A wet and dry vacuum can remove a lot of water quickly after a large spill. Check the carpet by pressing a dry cloth into the pile, and wait until the cloth comes out dry before you walk on it.

Preventing pet accidents

• Keep litter trays and food bowls away from carpeted areas.
• Use a pet-safe enzyme cleaner as a regular monthly treatment in the areas where the pet spends time.
• Take pets outside regularly, and reward them when they go in the right place.
• Consider a washable mat or a hard-floor area in the room where the pet is most likely to have accidents.
• Get the pet checked by a vet if the accidents start suddenly, because a change in urination can signal an illness.

Common mistakes

• Rubbing the stain. It spreads the stain and pushes it deeper.
• Using hot water on protein stains, which can set them.
• Using ammonia or an ammonia cleaner on urine, which encourages repeat marking.
• Using too little enzyme cleaner. The product needs to reach the underlay.
• Leaving the carpet damp. Damp carpet grows mold and brings the smell back.

When to call a professional

Call a carpet specialist if the smell persists after several careful treatments, if the stain has soaked through to the subfloor, or if the carpet is old and the padding has broken down. A specialist has equipment that can extract urine and water from deep in the carpet, and they can check the subfloor for damage. A professional clean is also worth considering if the carpet is valuable, or if a large area has been soaked.